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PHP项目职责链与处理

wen PHP项目 215

PHP 职责链模式详解

职责链模式（Chain of Responsibility）是一种行为设计模式，允许将请求沿着处理链传递，直到有处理器能够处理它。

PHP项目职责链与处理

基础概念

<?php
// 抽象处理器
abstract class Handler {
    protected $nextHandler = null;
    public function setNext(Handler $handler): Handler {
        $this->nextHandler = $handler;
        return $handler;
    }
    public function handle($request) {
        if ($this->nextHandler) {
            return $this->nextHandler->handle($request);
        }
        return null;
    }
}
// 具体处理器
class ConcreteHandler1 extends Handler {
    public function handle($request) {
        if ($request >= 0 && $request < 10) {
            return "Handler1 处理了请求: $request";
        }
        return parent::handle($request);
    }
}
class ConcreteHandler2 extends Handler {
    public function handle($request) {
        if ($request >= 10 && $request < 20) {
            return "Handler2 处理了请求: $request";
        }
        return parent::handle($request);
    }
}
class ConcreteHandler3 extends Handler {
    public function handle($request) {
        if ($request >= 20 && $request < 30) {
            return "Handler3 处理了请求: $request";
        }
        return parent::handle($request);
    }
}
// 使用
$handler1 = new ConcreteHandler1();
$handler2 = new ConcreteHandler2();
$handler3 = new ConcreteHandler3();
$handler1->setNext($handler2)->setNext($handler3);
echo $handler1->handle(5);  // Handler1 处理了请求: 5
echo $handler1->handle(15); // Handler2 处理了请求: 15
echo $handler1->handle(25); // Handler3 处理了请求: 25

实际应用场景

1 日志记录系统

<?php
abstract class Logger {
    const INFO = 1;
    const DEBUG = 2;
    const ERROR = 3;
    protected $level;
    protected $nextLogger = null;
    public function setNext(Logger $logger): Logger {
        $this->nextLogger = $logger;
        return $logger;
    }
    public function log($level, $message) {
        if ($this->level <= $level) {
            $this->write($message);
        }
        if ($this->nextLogger) {
            $this->nextLogger->log($level, $message);
        }
    }
    abstract protected function write($message);
}
class ConsoleLogger extends Logger {
    public function __construct($level) {
        $this->level = $level;
    }
    protected function write($message) {
        echo "控制台日志: $message\n";
    }
}
class FileLogger extends Logger {
    public function __construct($level) {
        $this->level = $level;
    }
    protected function write($message) {
        echo "文件日志: $message\n";
    }
}
class EmailLogger extends Logger {
    public function __construct($level) {
        $this->level = $level;
    }
    protected function write($message) {
        echo "邮件日志: $message\n";
    }
}
// 使用
$consoleLogger = new ConsoleLogger(Logger::INFO);
$fileLogger = new FileLogger(Logger::DEBUG);
$emailLogger = new EmailLogger(Logger::ERROR);
$consoleLogger->setNext($fileLogger)->setNext($emailLogger);
$consoleLogger->log(Logger::ERROR, "发生严重错误");
// 输出：
// 控制台日志: 发生严重错误
// 文件日志: 发生严重错误
// 邮件日志: 发生严重错误

2 表单验证系统

<?php
abstract class Validator {
    protected $nextValidator = null;
    public function setNext(Validator $validator): Validator {
        $this->nextValidator = $validator;
        return $validator;
    }
    public function validate($data) {
        $result = $this->doValidate($data);
        if ($result['valid'] && $this->nextValidator) {
            return $this->nextValidator->validate($data);
        }
        return $result;
    }
    abstract protected function doValidate($data): array;
}
class RequiredValidator extends Validator {
    private $field;
    public function __construct($field) {
        $this->field = $field;
    }
    protected function doValidate($data): array {
        if (empty($data[$this->field])) {
            return ['valid' => false, 'message' => "{$this->field} 字段是必填的"];
        }
        return ['valid' => true];
    }
}
class EmailValidator extends Validator {
    private $field;
    public function __construct($field) {
        $this->field = $field;
    }
    protected function doValidate($data): array {
        if (isset($data[$this->field]) && !filter_var($data[$this->field], FILTER_VALIDATE_EMAIL)) {
            return ['valid' => false, 'message' => "{$this->field} 格式不正确"];
        }
        return ['valid' => true];
    }
}
class LengthValidator extends Validator {
    private $field;
    private $min;
    private $max;
    public function __construct($field, $min, $max) {
        $this->field = $field;
        $this->min = $min;
        $this->max = $max;
    }
    protected function doValidate($data): array {
        if (isset($data[$this->field])) {
            $length = strlen($data[$this->field]);
            if ($length < $this->min || $length > $this->max) {
                return ['valid' => false, 'message' => "{$this->field} 长度必须在 {$this->min}-{$this->max} 之间"];
            }
        }
        return ['valid' => true];
    }
}
// 使用
$required = new RequiredValidator('email');
$email = new EmailValidator('email');
$length = new LengthValidator('email', 5, 100);
$required->setNext($email)->setNext($length);
$data = ['email' => 'test@example.com'];
$result = $required->validate($data);
print_r($result); // ['valid' => true]
$data = ['email' => 'invalid'];
$result = $required->validate($data);
print_r($result); // ['valid' => false, 'message' => "email 格式不正确"]

3 权限控制系统

<?php
abstract class AuthorizationHandler {
    protected $nextHandler = null;
    public function setNext(AuthorizationHandler $handler): AuthorizationHandler {
        $this->nextHandler = $handler;
        return $handler;
    }
    public function authorize($user, $action) {
        $result = $this->doAuthorize($user, $action);
        if ($result['authorized'] && $this->nextHandler) {
            return $this->nextHandler->authorize($user, $action);
        }
        return $result;
    }
    abstract protected function doAuthorize($user, $action): array;
}
class AuthenticationHandler extends AuthorizationHandler {
    protected function doAuthorize($user, $action): array {
        if (!$user || !isset($user['id'])) {
            return ['authorized' => false, 'message' => '未登录用户'];
        }
        return ['authorized' => true];
    }
}
class RoleCheckHandler extends AuthorizationHandler {
    private $allowedRoles;
    public function __construct($allowedRoles) {
        $this->allowedRoles = $allowedRoles;
    }
    protected function doAuthorize($user, $action): array {
        if (!in_array($user['role'], $this->allowedRoles)) {
            return ['authorized' => false, 'message' => '没有权限访问'];
        }
        return ['authorized' => true];
    }
}
class RateLimitHandler extends AuthorizationHandler {
    private $limits = [];
    protected function doAuthorize($user, $action): array {
        $key = "{$user['id']}_{$action}";
        $this->limits[$key] = ($this->limits[$key] ?? 0) + 1;
        if ($this->limits[$key] > 100) {
            return ['authorized' => false, 'message' => '请求过于频繁'];
        }
        return ['authorized' => true];
    }
}
// 使用
$auth = new AuthenticationHandler();
$role = new RoleCheckHandler(['admin', 'manager']);
$rate = new RateLimitHandler();
$auth->setNext($role)->setNext($rate);
$user = ['id' => 1, 'role' => 'admin'];
$result = $auth->authorize($user, 'delete-post');
print_r($result); // ['authorized' => true]

职责链模式的高级应用

1 灵活的中间件系统

<?php
abstract class Middleware {
    protected $next = null;
    public function setNext(Middleware $middleware): Middleware {
        $this->next = $middleware;
        return $middleware;
    }
    public function handle(Request $request): Response {
        $response = $this->process($request);
        if ($response === null && $this->next) {
            return $this->next->handle($request);
        }
        return $response;
    }
    abstract protected function process(Request $request): ?Response;
}
class Request {
    public $headers = [];
    public $body = [];
}
class Response {
    public $status = 200;
    public $body = '';
    public $headers = [];
}
class CorsMiddleware extends Middleware {
    protected function process(Request $request): ?Response {
        // 处理CORS
        if (!isset($request->headers['Origin'])) {
            return new Response();
        }
        $response = new Response();
        $response->headers['Access-Control-Allow-Origin'] = '*';
        return $response;
    }
}
class AuthMiddleware extends Middleware {
    protected function process(Request $request): ?Response {
        if (!isset($request->headers['Authorization'])) {
            $response = new Response();
            $response->status = 401;
            $response->body = json_encode(['error' => '未授权']);
            return $response;
        }
        // 验证token...
        return null; // 继续下一个中间件
    }
}
// 使用
$middleware = new CorsMiddleware();
$middleware->setNext(new AuthMiddleware());
// 动态添加中间件
$middleware->setNext(new class extends Middleware {
    protected function process(Request $request): ?Response {
        // 日志记录
        return null;
    }
});

最佳实践

  1. 明确职责边界：每个处理器应该只负责单一职责
  2. 可选的链结构：允许动态添加或移除处理器
  3. 默认处理：在链的末端添加默认处理器
  4. 性能考虑：避免过长的链影响性能
  5. 异常处理：确保链中的异常能够被适当处理

优缺点

优点：

  • 降低耦合度
  • 增强灵活性
  • 符合开闭原则
  • 简化对象职责

缺点：

  • 性能影响
  • 调试困难
  • 可能导致请求被忽略
  • 不保证请求一定被处理

职责链模式特别适合处理那些需要多个处理器按顺序处理的场景,如日志系统、验证系统、权限系统等。

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